„I have one life and one chance to make it count for something... My faith demands that I do whatever I can, wherever I am, whenever I can, for as long as I can with whatever I have to try to make a difference.“

— Ursula Goodenough American biologist 1943Context: We all eat or are eaten. That's the way life works, it's a greater rhythm. And that's why science and the understandings it has uncovered can be a source of joy.
This all relates to assent, a very important Judeo-Christian concept. "Thy will be done" is a God-kind of assent. "God works in mysterious ways," and you're supposed to give assent even if you don't like it. As a religious naturalist, I think of assent differently. Assent is saying, "Okay, for whatever reason, this is the way life works. It's an acceptance of what is. After that fundamental acceptance, I can live my life to minimize suffering and promote as much as good as I can, and try through whatever work I do to help others." We can't get around death, but we can get around poverty. We can try to avoid women being brutalized. We can curb environmental degradation.
One can start from the perspective of a religious naturalist or from the perspective of the world religions and arrive at the same place: a moral imperative that this Earth and its creatures be respected and cherished.

— Edward Everett Hale American author and Unitarian clergyman 1822 - 1909Statement published in A Year of Beautiful Thoughts‎ (1902) by Jeanie Ashley Bates Greenough, p. 172, Third statement for June 11. This has often been misattributed to Helen Keller in some published works since at least 1980, perhaps because she somewhere quoted it.
Variant:
I am only one,
But still I am one.
I cannot do everything,
But still I can do something;
And because I cannot do everything,
I will not refuse to do the something that I can do.
The Book of Good Cheer : A Little Bundle of Cheery Thoughts‎ (1909) by Edwin Osgood Grover, p. 28; also in Masterpieces of Religious Verse (1948) by James Dalton Morrison, p. 416, where it is titled "Lend a Hand"

— Helen Keller American author and political activist 1880 - 1968Edward Everett Hale in a statement published in A Year of Beautiful Thoughts‎ (1902) by Jeanie Ashley Bates Greenough, p. 172; <!-- and perhaps as early as an edition of Ten Times One is Ten (1870) by Hale--> This has been misattributed to Keller in published works since at least 1980. Keller and Hale were good friends, and letters to Hale can be found in her youthful autobiography The Story of My Life (1902). In 1910 Keller dedicated her poem "The Song of the Stone Wall" to Hale who had died in 1909.

— Hillary Clinton American politician, senator, Secretary of State, First Lady 1947Context: I am not a natural politician, in case you haven’t noticed, like my husband or President Obama. So I have a view that I just have to do the best I can, get the results I can, make a difference in people’s lives, and hope that people see that I’m fighting for them and that I can improve conditions economically and other ways that will benefit them and their families.